This study investigated the course of insomnia from young adolescence to adulthood, and identified early predictors of adult insomnia. Data on sleep, health, and lifestyle factors were collected in 1242 individuals at four time points from at age 13 years to 30 years, in a Norwegian general sample. There was a high stability of sleep problems: of participants with DSM-IV defined insomnia at age 30, 58%, 29%, and 39% also reported sleep problems at age 23, 15 and 13, respectively. Poor health during adolescence was the strongest predictor of adult insomnia, and the strongest individual predictors were pain, poor perceived health, diffuse symptoms, and previous sleep problems. We conclude that insomnia is persistent over time from young adolescence to adulthood, and that several health factors during adolescence predict insomnia at age 30.